The present disclosure relates to devices for feeding solid particles into a fluid stream and particularly a pressurized stream of air such as that employed for blasting or cleaning operations where it is desired to inject solid particles for effecting abrasion on the article to be cleaned by the fluid stream. A particularly widely employed application of such devices is that of feeding solid carbon dioxide or dry ice particles into a pressurized air stream for blast cleaning of particles or items to be cleaned and recycled in a manufacturing or assembly operation. Such devices for introducing particles into a fluid stream are often referred to as “air-lock valves.” Dry ice fluid blasting is widely used for cleaning metal parts to be used in manufacturing or reconditioning of components, these items can be found in the automotive, electrical, nuclear, and printing industries.
Heretofore, vane type devices have been employed for feeding dry ice particles into a pressurized air stream; and, problems have been encountered in providing sealing of the pressurized fluid from the feeding chamber for the dry ice particles and particularly as the feeder device is lowered to the temperature of the dry ice of about −110° F. (350° R). Typically, the feeder mechanism is operated by a motor to rotate the vane or disc member for introduction of the dry ice particles into the flow stream. Another type of feeder mechanism employed for feeding dry ice particles into a fluid stream is that of a cylindrical rotary member; however, feeder mechanisms of this type have also encountered problems of sealing about the injection port to the fluid pressure chamber and the cylindrical rotor member at the extremely low temperatures encountered where dry ice is fed into the fluid stream. Heretofore, where increased pressure was applied to the seals for effecting sealing to overcome the contraction of the feeder components, the increased friction required prohibitive increases in power to the motor employed for rotating the vane, disc or rotary cylinder. Thus, it has been desired to provide a feeder device for injecting particles into a fluid stream, particularly for injecting dry ice into a pressurized air stream, in which effective sealing is provided at the extremely low temperatures encountered with dry ice and in such a manner as to eliminate the need for excessive power to the motor for rotating the feeder mechanism.